It is desirable to provide ventilation for the areas beneath building roofs to reduce the accumulation of heat and to reduce the accumulation of moisture in the attic or other spaces immediately below the roof, for example. In providing ventilation, it is important to prevent the entry of water into the building structure through the vent. Also, it is desirable to prevent debris and small animals from entering the building structure though the vent. Ultimately, the benefits of a properly constructed roof vent will prolong the life of the roof, virtually eliminate leaks caused by ice dams, reduce cooling bills, and reduce moisture build up in the attic that can lead to rot.
To protect buildings and their contents from water damage, roofers repair and install roofs made of tar, asphalt and gravel; rubber, thermoplastic; metal; or shingles made of asphalt, slate, fiberglass, wood, tile, or other material. There are two types of roofs—flat and sloped. Slope is the change in roof height for a horizontal distance for every 12 inches of horizontal distance (e.g., “flat slope” is about 0 to about 2 inch vertical distance for every 12 inches of horizontal distance and a “steep slope” is a greater than 2 inch vertical distance for every 12 inches of horizontal distance). Many commercial, industrial, and apartment buildings have flat or slightly sloping roofs for drainage (i.e., roofs with minimum slope of less than about 2 inches of vertical distance for every 12 inches of horizontal distance). Many residential houses have steep sloped roofs having a larger slope.
Flashings have been used for decades to weatherproof roof penetrations. Flashings protect the roof where moisture could get under it, such as at joints in the roof, places where a vent pipe or chimney pokes through, a valley where two roof surfaces meet, or where a roof meets a wall. Some flashings are installed before the roofing goes on, others are put in place along with the roofing. Flashing is widely used with shake, composite and wood shingles and roll roofing. Like many flashing pieces, the vent flashings are often “weaved” between shingle courses.
Flashings for pipes and other roof penetrations extending out of a roof exhaust source are often constructed from thin sheet metal that is cut and formed into the desired shape. The flashing is often formed from one piece of sheet material that has a central opening cut therein to fit about the roof penetration. Thereafter, a sealing material, such as caulk or tar, is applied proximate the juncture of the roof penetration and the central opening in the sheet material.
Roof vents (or turbine vents) come in many forms, but generally include some type of weather-shedding hood and a flange around the base that forms a seal between the vent and the surrounding roofing material. Some vents have a pipe that penetrates the roof surface and is exposed above the roof. Also, some vents have a tubular outside vent stack cover which is secured to a substantially flat roof flashing base plate. See, for example, U.S. Pat. No. 5,778,611 to Michel, “Vent Extension Flashing Assembly”, issued Jul. 14, 1998. In other roof vents, the pipe remains exposed through the base plate flashing assembly. See for example U.S. Pat. No. 4,333,660 to Cupit, “Seal Device for Pipe Projecting through Roof”, issued Jun. 8, 1982. Ultimately, to make a roof vent installation watertight, the most common technique is to “weave” or cover the vent flanges with roof material on the high side towards the roof ridge and along the edges of the vent, and cover the roofing material with the vent flange on the low side.
Known roof vents are typically assembled from essentially planar sheet material so that a portion of the sheet material about the central opening lies in approximately the same plane as the remaining portion of the sheet material. Such construction can lead to an increased likelihood of leakage at the central opening. An example of such a roof vent is disclosed in U.S. Pat. No. 4,570,396 to Struben, “Roof structure for mobile homes”, issued Feb. 18, 1986.
The present invention addresses problems and limitations associated with the related art.